Fix positioning issues with browse files button

Issue is that in Firefox clipboard is blocking the browse files
from moving all the way to the right.
Move clipboard up 1px into -1px to unblock "browse files"

SS from firefox:

![Screen_Shot_2016-01-18_at_4.01.58_PM](/uploads/312a5f1e55ca707081f718e2413416fb/Screen_Shot_2016-01-18_at_4.01.58_PM.png)

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/10849


See merge request !2489